Trenchless methods for structural renovation of drinking water pipelines include the pipe in pipe method, pipe bursting method, and polyethylene thin wall lining method. As described in U.S. Pat. No. 7,189,429, these methods are disadvantaged by their inability to deal with multiple bends in a pipeline and the fact that lateral connection pipes to customers' premises have to be disconnected and then reinstated after execution of the renovation process.
U.S. Pat. No. 7,189,429 describes a method of forming a coating on the internal surface of a drinking water pipeline, the method comprising the steps of: a) providing a liquid, two-part coating system; b) mixing together the first part and the second part to form a mixture, and c) applying the mixture as a coating to said surface so as to form, at high cure rate, a monolithic lining which exhibits high strength and flexibility. Preferably the two parts of the system are applied through heated airless spray equipment. Such equipment may, for example, include a centrifugal spinning head or a self-mixing spray gun assembly.
U.S. Pat. No. 6,730,353 describes a coating for drinking water pipelines. The two-part coating system comprises a first part comprising one or more aliphatic polyisocyanates, optionally blended with one or more amine reactive resins and/or non reactive resins, and a second part comprising one or more aromatic polyamines optionally blended with one or more oligomeric polyamines, such that the two parts, when mixed together and applied to the internal surfaces of pipelines, form a rapid setting impervious coating suitable for contact with drinking water.
WO2010/120617 describes methods of forming a coating on (e.g. internal) surfaces of a (e.g. drinking water) pipeline with two-part coating compositions comprising a first part comprising at least one polyisocyanate and a second part comprising at least one aspartic acid ester. Also described is a reactive two-part coating composition that comprises a first part comprising at least one polyisocyanate; and a second part comprising at least one aspartic acid ester and at least one aromatic amine that is a solid at 25° C.